Tagged Questions

Electrostatics is concerned with the field and potential of stationary electrical charges and electric charge distributions. Problems are this type are almost exclusively concerned with mathematics of geometries using the inverse-square law.

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protons and electrons can have different charges?

I'm studying physics (self-learning) and I'm a bit confused with Columbs law. q1 and q2 are just particles (electrons or protons). 1 proton has a charge of 1.602 * 10^-19 C 1 electron has a ...
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0answers
12 views

Why potential difference (V) increases with increase in the length of conductor? [on hold]

Why potential difference (V) increases with increase in the length of conductor? Please explain it in an easy way. Two conductors A and B are of length 2 m and 5 m and have potential difference ...
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2answers
26 views

Using Coulomb's law to solve for a continuous charge distribution [on hold]

I have been trying to evaluate this specific integral and have been completely stuck. $\frac{1}{4\pi \epsilon_0} \int^L_0 \frac{2\lambda z}{(x^2+z^2)^\frac{3}{2}}dx$ I am a freshman and have been ...
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1answer
7 views

discharging static

Quick question, if you have a buildup of static charge causing sheets of paper to stick together, can you have a grounding foil touching the paper to dissipate the charge to prevent pages from ...
1
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0answers
35 views

Electric field at a point [on hold]

We consider a thin disk whose center is $O$ and radius is $R$, which has an electric surface charge density of $\sigma$. We want to find the expression of the electric field $\vec{E}$ at a point ...
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13 views

Determining charge type by looking at electrometer measures

Suppose we have 2 concentric Faraday cages (they do not touch at any point). The outer cage is grounded. If we were to put a charge inside the inner cage and measure voltage between cages, what sign ...
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1answer
33 views

Electric field and potential between two charges [on hold]

There are two point charges on the $x$ axis and $x'$ is a place where the potential, relative to infinity, is the biggest. Why is the electric field zero at this point?
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29 views

Electric field in a “concave” conductor

I am aware that the electrons are distributed across charged conductor surface so that the areas with smaller radius of curvature have more charge per surface area. But what happens when the ...
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0answers
29 views

Calculate electric field without using Gauss law

Given a uniformly charged sphere ( total charge $5 nC$ ) of radius $R=10 cm$, write the equation of electric field vector for any distance $r (r > R)$ from sphere center and calculate total ...
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0answers
13 views

Addition of forces in dielectric material

In this paper (page 2 of document) it is said that: Because this calculated force was comparable to the gravitational force, they assumed that the same would be true for the forces on a ...
2
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3answers
50 views

Calculate the flux of a point charge with Gauss's law

I know from my class that to calculate the flux of a point charge with Gauss's law, I have to make a surface that intersects with all of the flux lines resulting from the charge, and then make this ...
0
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1answer
19 views

Finding voltage between two points in space

If electric field vector is defines as : $\vec{E} = \frac{V_0x^2}{a^3} \vec{i_x} + \frac{V_0y}{a^2} \vec{i_y} $ where $V_0 $ and $a$ are known constants, $\vec{i_x}$ and $\vec{i_y}$ unit vectors of ...
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0answers
17 views

Electric Field Resulting from a Conductor

In preparation for an upcoming exam, I've been attempting to visualize the electric field produced by a conductor in a variety of situations. I asked myself the following question and attempted to ...
0
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1answer
58 views

The “classical radius” of the electron [closed]

According to one theory, the mass m of the electron arises simply as a consequence of the electrostatic energy of its electric field, through Einstein's famous expression ε=mc^2, where ε is the field ...
0
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1answer
34 views

Net Electric Field of Multiple Charges [closed]

Question: Four charges, each of magnitude +Q are placed at the corners of a square of side a. Obtain an expression for the electric potential at the centre of the square and at the mid point of one ...
0
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1answer
33 views

Why is voltage multiplied when batteries are connected in series but not in parallel?

As i understand, the different voltage between two object is caused by the total different charged between two object. Thus, the higher extra electron between two opposite charged object, the higher ...
1
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1answer
70 views

How does EM radition depend on the reference frame?

In special relativity, magnetism is electrostatics in a different reference frame. This is how we explain the magnetic field being produced by moving charges (aka currents). Charges that move produce ...
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1answer
33 views

Show the equivalence of two electrostatic energy

$$U = \frac{1}{2}\iint_{all space}^{ } \frac{\rho(1)\rho(2)}{4\pi\epsilon_{0}r_{12}}dV_{1}dV_{2} $$ and $$U = \frac{\epsilon_{0}}{2}\int_{allspace}^{ } \vec{E} \cdot \vec{E} dV.$$ In the left ...
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1answer
56 views

Relationship between polarization density and electric field

Imagine I have an electric field $E$ created due to some free charges. Then I introduce a dielectric material somewhere. What confuses me is the polarization field $P$, which is now proportional to ...
0
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1answer
46 views

Why does the earth suck both positive and negative charges?

If the earth is a bit negatively charged, it is understood that it can take away the positive charges of a positively charged body when grounded. Why does it take away the extra electrons of a ...
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0answers
26 views

Electric field of Symmetric Parts [closed]

So I'm preparing for a test and one thing that I haven't seen examples of, but know is possible is using Gauss's Law on objects that have symmetric parts. I made up the following question: Find ...
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3answers
35 views

Deriving relationship between distance and angle for field of a line charge

The relationship $r\,\mathrm{d}\alpha = \mathrm{d}x \cos(\alpha)$ is not obvious to me. In fact, when I look at it, I think it should be $r\,\mathrm{d}\alpha \cos(\alpha) = \mathrm{d}x$. Can someone ...
0
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0answers
30 views

Vector of electric field

I have a triangle whose points are in $A(0,0,0)$, $B(a,0,0)$ and $C(0,a,0)$. The edges of this triangle are uniformly charged with value $Q'$ and everything is in vacuum. I need to find the vector of ...
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1answer
27 views

Why in PN junctions the octet rule is dominating electrostatic repulsion?

The depletion region in PN junctions is created by charges from the N part diffusing into the P part, thus completing an octet of covalent bonds in the P part. This shift however leaves positive ions ...
1
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1answer
34 views

Capacitance in a parallel plate cap with the real electric field

In many books of general physics, they prove the equations for capacitance of a cap of parallel plates as if the electric field where constant everywhere but what would happen if we take the real ...
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3answers
50 views

Finding charge density from from differential form of gauss law

I didnt get why he didvided and multiplied by r^2.This question is from d j griffith .
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0answers
20 views

Divergence in interaction between induced dipoles

Suppose I have two polarizable point-particles 1 and 2 arranged on the z-axis and separated by $r$. Each particle has a dipole moment $\mathbf{p}_i=\alpha \mathbf{E}_i$. If we apply an external field ...
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3answers
54 views

Potential due to a continuous charge distribution on ring

Derive the formula for the potential at point $P(0,0,z)$ directly above the center of a ring of charge with radius $R$ and uniform charge density $\lambda$. My attempt: Since $$\lambda= ...
0
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1answer
44 views

How is it possible for an infinitely large charged plane to cause the same electric field regardless of distance? [duplicate]

Assume there is an infinitely large plane with a charge density $\sigma$. I understand how to derive, using Gauss' Law, that $E = \frac{\sigma}{2\epsilon_0}$ is the electric field at a distance $r$ ...
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2answers
32 views

Confusion with Grounded Conductor: bringing in a point from infinity

Suppose, for sake of argument, we have a spherical grounded conductor at the origin. Additionally, let our reference voltage be at infinity. Now, I view the potential of a point in space as being the ...
2
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0answers
77 views

Differential equation of a Green function for a dielectric with a charge [closed]

adding Suppose there are two infinite planes, one in $z=a$ and the other in $z=b$, with $a<b$. Between the planes, there is a dielectric medium with constant $\epsilon_1$. The differential equation ...
0
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2answers
36 views

Gauss law in integral form

Scanning through the lecture notes of my professor I came across some confusing definition, that he calls "Gauss law in a global form" which has the following representation ...
1
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1answer
75 views

Zero divergence of Electric field

I'm trying to rigorously derive the integral form of Gauss's law from Coulomb's law and the divergence theorem. Arrive at $$ \oint\limits_{\partial V} E\cdot da = \begin{cases} \frac ...
0
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1answer
36 views

Field and Charge densities in two dimensional corners and along edges

In jackson's book, we can derive the equation as following. $\sigma(\rho)=\epsilon_{0}E_{\phi}(\rho, 0)\approx-\frac{\epsilon\pi a_{1}}{\beta}\rho^{(\pi/\beta)-1}---(2.75)$ My question is there are ...
1
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1answer
30 views

Help regarding understanding derivation of electrostatic potential in a solution to a problem

I was looking at the solution of finding the energy stored in a charged solid sphere in which the electric field was and then later stated the electrostatic potential is I understand that to ...
0
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2answers
37 views

Equivalent formulas for electric current density

I am reading an article that states that the "ratio of current to the area for a given surface is known as current density" and is defined as $J = \frac{I}{A}$ where $I$ is the current and $A$ is ...
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1answer
22 views

2 spheres both negative or positive [closed]

Two small charged metal spheres A and B are situated in a vacuum. The distance between the centres of the spheres is 12.0 cm, as shown in Fig. 4.1. The charge on each sphere may be assumed to be a ...
1
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1answer
34 views

What is the purpose of the metal strip??

Context: Two large, flat metal plates are held parallel to each other and separated by a distance $d$. They are connected together at their edge by a metal strip. A thin plastic sheet ...
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0answers
25 views

Is there a charge across all space? [duplicate]

We're studying electrostatics in class, and the teacher introduced us to Gauss' Law a few days ago as $$\int \vec{E} \cdot \mathrm{d}\vec{A} = \frac{Q}{\epsilon_0}$$ Now suppose that the entire ...
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1answer
17 views

Two uniformly charged spheres are superposed with slight displacement. What's the surface density?

*Note: This is from the Second Volume of Feynman's Lectures on Physics : Mainly Electromagnetism and Matter And this is the excerpt from the book: If the relative displacement of the two spheres ...
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0answers
28 views

What is the electric field near an infinite sheet with a point charge near by? [closed]

The electric field near a negatively charged conducting infinite sheet is $\frac{-\sigma}{2\epsilon}$. If we add an equally charged positive particle some distance $r$ away from the sheet, the field ...
1
vote
1answer
30 views

Can a human be killed by electro-static discharge while performing daily chores? [closed]

During freezing-winter seasons, as soon as I reach my office and get off the warm-clothing; I get an electrostatic discharge whenever I touch a metallic water-fountain in my lab. The shock I get is ...
0
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1answer
33 views

Parallel plate capacitor

How does a parallel plate capacitor emit a constant electric field between its plates? Isn't the electric field governed by an inverse square law? Then what would happen if I put a charged particle ...
0
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2answers
30 views

In low voltage (3-12V) DC applications, which is safer to be exposed or touchable + or - terminal?

The - side has a surplus of $e^{-}$s and the opposite is true for the + side of the power supply. Does it not matter, or depends on your configuration / contact with Earth? Please explain!
0
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3answers
97 views

How does an electron undergoing uniform circular motion exactly lose energy?

One of the main reasons for the failure of the Rutherford model of atomic structure, it is famously stated, is that the electron undergoing circular orbit loses energy since due to its centripetal ...
0
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0answers
45 views

Does Gauss' Law apply to real physical solid conductors?

In a conductor there is no electric field because there is no charge. There is no charge inside because any charges present inside would repel each other and be driven to the surface of the conductor. ...
0
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1answer
17 views

Binding Energy of an Electric Dipole

My question is structured in two parts: Is there any way to isolate the charges of an electric dipole? What is the binding energy of an electric dipole? To put it in another way, is there ...
2
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3answers
86 views

How come we talk about gravitational potential energy and not gravitational potential?

With regards to gravity the equation learned is $$U=-\frac{GMm}{r}$$ And the relationship to force is $$F=-\frac{dU}{dr}$$ In electrostatics we instead talk about electric field and electric ...
1
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1answer
29 views

Does magnitude of a charge influence magnitude of force that individual charge exerts on another charge [closed]

two point charges, q1 and q2, are placed 0.3m apart on the x-axis, as shown in the figure above. Charge q1 has a value of -3 nano Coulomb and q2 has a value of +4.8 x10^-8 C. The net electric field ...
2
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2answers
57 views

Is a given charge density a surface charge density or volume charge density?

The exact question goes like this: In a certain electronic tube, electrons are emitted from a hot plane metal surface, and collected by a plane metal plane parallel to the emitter, at a distance ...